...as

  OStringBuffer b("foo"); b = "bar" + b;

doesn't work as one might expect (see the mail thread starting at
<https://lists.freedesktop.org/archives/libreoffice/2016-October/075464.html>
"concat of OUStringBuffer".  That feature was LIBO_INTERNAL_ONLY, anyway.  And
of the affected places, MethodDescriptor::getSignature
(codemaker/source/javamaker/javatype.cxx) was the only one that would actually
have benefitted.

Change-Id: Ib84266f43e40c42c2e428f0c0616db8cfa90adff